1. Field of the Invention
The present invention relates to a semiconductor device that includes a spin transistor having a MOS structure.
2. Related Art
The advent of ultrahigh-speed and high-functionality semiconductor devices had spurred rapid evolution of an information-oriented and knowledge-intensive society into a global web of high-speed communication networks, as exemplified by the ubiquitous presence of radiofrequency cellular or “mobile” phones in daily lives. Naturally, the world-wide spread of such social transformation, as well as an insatiable quest for more efficient and convenient life-styles, demands yet higher performance of semiconductor devices that are integrated on a single chip on an ever-larger scale, to realize a system-on-chip versatile architecture providing almost every conceivable functionality.
Unfortunately, however, in order to speed-up their operation, simply miniaturizing the physical dimensions of the principal components of the large scale integration (LSI) circuit, i.e., metal insulator semiconductor field effect transistors (MISFETs), or more specifically, metal oxide semiconductor field effect transistors (MOSFETs) is becoming a increasingly difficult task to achieve. It is believed that, such straightforward approach towards high-speed operation by shrinking dimension will soon encounter not only practical problems but also fundamental physical limitation as a way of achieving high-performance LSI.
Under these circumstances, a new approach to realize higher-performance electronic circuits by adding new sophisticated functionality to the conventional complementary silicon MOSFETs (C-MOSFETs) circuits is much desired.
In fact, an increasing attention is now directed towards the study of spin electronics, which utilize the spin degree of freedom of electrons, in addition to their electrical charges.
Particularly, a spin transistor having a MOSFET structure is thought to be a prime candidate of such a value-added higher-performance electronic device, thanks to its structural and functional compatibility with the prevailing conventional complementary silicon MOSFETs (C-MOSFETs) circuits.
Whereas the operation of the conventional MOSFETs is regulated simply by the electric charges flowing through the channel, the operation of the spin transistor having a MOSFET structure (hereinafter, referred to as the spin-MOSFET) is made to depend also on the spin of the channel carriers (see IEEE Trans. ED 54 (2007), p 961, by M. Tanaka and S. Saguahara, for example). Therefore, as a value-added versatile MOSFET, the spin-MOSFET can be easily and conveniently integrated into a current C-MOSFETs circuit, while providing additional sophisticated functions to the conventional circuit.
Nonetheless, as will be described later, the spin-MOSFET is not a problem free option for realizing higher-performance electronic circuits. As will be explained below, it is difficult to form a nonvolatile and reconfigurable logic circuit by a spin-MOSFET, while maintaining stable and reliable device operation and, at the same time, retaining the compatibility with the conventional C-MOSFET circuits.